If you're in year 29 it's less likely than year 25 or less, but run the numbers to check.also refi, as long as it's primary res and loan bal isn't over the recent tax change limit then interest should still be deductible. 

For one, you have a limited time period to find a new property, which could leave you in a vulnerable position from a negotiation standpoint.

I really want to maximize a buy/hold/refinance or BRRRR type strategy; from my limited knowledge, I've heard US markets are more amenable to that strategy.

Harrisburg is a good cash flowing market, but it is very block by block in the city limits. 

The structure is a business expense and has a limited life.

I had to jump through some hoops but just closed on refinancing my investment property HELOC with PenFed Credit Union and they gave me the $200k limit I was looking for. 

I have limited experience with 403B loans, but from what I can tell they can only borrow up to $50K, and they have up to 5 years to pay it back with interest (up to 5%).

I know there is the one BP guy who states it is surrounded by gov lands and that limits supply but within that space there is still much room to go.

My effective rate once typical fees (origination, appraisal, PMI etc) are removed is closer to 4.25%,  I also stay off the fannie 4 or 10 loan limit radar with owner-financing.  

For VA loans, alas loan limits do not scale up like that without a down payment.